https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80559
--- Comment #2 from Matt Godbolt <matt at godbolt dot org> --- Thanks: it seems the command-line parameter `-std=c++1z` is needed to trigger the segfault. https://godbolt.org/g/6oDO6X Apologies for not realising this in the initial report.